Hata-Yanagiya physical activity calculation system: a novel global positioning system-based method for accurate estimation of oxygen consumption during walking and running.

Introduction: Marathon running has become increasingly popular among amateur athletes, many of whom maintain speeds of 8-9 km/h. However, existing methods for estimating oxygen consumption (VO₂) during running and walking-such as the American College of Sports Medicine (ACSM) equations and commercial activity monitors-often lack accuracy and transparency. This study introduces the Hata-Yanagiya Physical Activity Calculation (HYPAC) system, a novel approach for estimating VO₂ using Global Positioning System (GPS) and map data.

Methods: The HYPAC system was developed through regression equations based on metabolic equivalents (METs) and slope data. To validate the system, 10 university students (5 runners, 5 non-runners) completed a 5 km course while equipped with a GPS device and a portable metabolic measurement system. VO₂ estimates from the HYPAC system were compared with measured values and those calculated using ACSM equations.

Results: The HYPAC system demonstrated high accuracy in estimating VO₂, with a relative error of -0.03 [95% confidence intervals (CI): -0.14, 0.08] compared to measured values. For the running group, the HYPAC system achieved the lowest absolute mean relative error (0.02). In the mixed running/walking group, the HYPAC system maintained strong performance with a relative error of -0.07 (95% CI: -0.26, 0.12).

Discussion: The HYPAC system provides a transparent and accurate method for estimating VO₂ during walking and running, outperforming existing methods under varied conditions. Its open-source framework encourages further validation and improvement by researchers and practitioners. Future studies should address limitations such as sample size and population diversity to enhance the system's applicability.